Climate Change

Turning up the heat

Climate has changed greatly over geological timescales, as we shall see in Chapter 2. But what is of immediate concern is that climate has shown an almost unprecedented rapid global warming trend in the last few decades. Since the start of reliable observations in the nineteenth century, scientists from weather services and research laboratories in many countries have examined local, regional and global average surface air and water temperatures, on land and from ships. The World Meteorological...

Why climate projections are different

Numerical prediction of climate is a different problem, even though it starts with the same equations governing atmospheric motion and continuity of matter (the amount of air and water in the atmosphere). There are two main differences First, climate projections are not about predicting the exact weather at any time in the future, but rather about projecting the statistics (average behaviour and variability) of the future weather. This reduces the relevance of short-term chaotic behaviour in...

What climate changes are likely

In terms of key environmental parameters, the Earth system has recently moved well outside the range of natural variability exhibited over at least the last half million years. The nature of changes now occurring simultaneously in the Earth System, their magnitude and rates of change are unprecedented and unsustainable. Paul Crutzen (Nobel Laureate) and Will Steffen (International Geosphere-Biosphere Programme, Executive Director), 2003. The complexity of the climate system makes it difficult...

The emissions scenarios used by the IPCC

In order to provide policy-relevant advice on the consequences of human-induced climate change in the twenty-first century, the IPCC commissioned a range of scenarios of greenhouse gas and sulfate aerosol emissions up to the year 2100. These emission scenarios were developed by a panel of authors, with wide consultation, and an open process of review and comment by experts and governments, followed by subsequent revisions. The scenarios were reported in the Special Report on Emissions Scenarios...

Forecasting the weather

Foresight is routinely used in regard to the weather, and affects many of our day-to-day decisions. It is therefore useful to compare the basis for weather forecasting with that for climate projections, in order to understand both what they have in common and what the differences are. Weather forecasting used to be based on experience with past situations, which developed into changed weather patterns that experts could either remember or look up from past records. This was called 'analogue...

From polarisation to probability and risk

People respond in different ways to uncertainty. Sometimes they get confused and see it as a reason for concluding that they know nothing useful on the subject, and therefore see no reason to act. This is especially the case if action would have obvious costs, and is the position taken by many who challenge the reality of human-induced climate change. These people in denial tend to focus on the uncertainties rather than on what is known. Some (but not all) may have a vested interest (financial...

The need for and nature of foresight

While I am not a fan of Donald Rumsfeld, I think the quote above from one of his news briefings drew some rather unfair lambasting. It summarises, if one concentrates on its meaning and applies it to climate change, some important aspects of the science of climate change as well as defence policy questions. That is, there is a whole range of aspects of climate change, with some much more certain than others. There are also uncertainties and possibilities we are aware of, and may even be able to...